Findings related to IL-8 and IL-10 gene polymorphisms in a Mexican patient population with irritable bowel syndrome infected with Blastocystis

The intestinal protozoan parasite Blastocystis is one of the most common parasites worldwide in humans and, although its ability to cause human disease has been questioned, some reports have demonstrated that this microorganism is associated to the development of irritable bowel syndrome (IBS) and to a proinflammatory response, in which the expression of some cytokines is unregulated. Since inflammatory cytokine gene polymorphisms might have a role in the pathophysiology of IBS, we assessed the role of single nucleotide polymorphisms (SNPs) for interleukin (IL)-8 and IL-10, in previously collected DNA samples from IBS patients and controls, with or without Blastocystis infection. IL-8+396(G) and IL-10-1082 (A) alleles (p = 0.0437 and p = 0.0267, respectively), as well as their homozygous (p < 0.0001 and p = 0.0039, respectively) and IL-8+781(CT) (p = 0.0248) genotypes were significantly overrepresented in patients with IBS in comparison with controls. IL-8+396(GG) genotype was relevant because it was associated to IBS (p < 0.0001), to Blastocystis (p = 0.0025), and to IBS-Blastocystis (p = 0.0272). In the latter binomial association, this genotype presented a high contribution (etiological fraction = 0.452) and a risk > fourfold to develop IBS. IL-8+781 (T) and IL-10-592 (C) alleles were also associated to Blastocystis and to IBS-Blastocystis, respectively (p = 0.0448 and p = 0.0166). Our results suggest that some IL-8 and IL-10 SNPs could change individual susceptibility increasing the relative risk in the development of IBS in Blastocystis carriers.